Unit 2 Test Questions

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All questions to be used for the test need to be made by Tuesday :)

1.When a catalyst is added to a system at equilibrium, a decrease occurs in the (1-11 Vlad and Peter)
a) activation energy <--Correct Answer
b) heat of reaction
c) potential energy of the reactants
d) potential energy of the products
e) nothing

2. Which statement describes characteristics of an endothermic reaction?
a) The sign of H is positive, and the products have less potential energy than the reactants.
b) The sign of H is positive, and the products have more potential energy than the reactants. <--Correct Answer
c) The sign of H is negative, and the products have less potential energy than the reactants.
d) The sign of H is negative, and the products have more potential energy than the reactants.

3. Which statement explains why the speed of some chemical reactions is increased when the surface area of the reactant is increased?
a) This change increases the density of the reactant particles.
b) This change increases the concentration of the reactant.
c) This change exposes more reactant particles to a possible collision. <--Correct Answer
d) This change alters the electrical conductivity of the reactant particles.

4. Which conditions will increase the rate of chemical reaction?
a) Decreased temperature and decreased concentration of reactants?
b) Decreased temperature and increased concentration of reactants?
c) Increased temperature and decreased concentration of reactants?
d) Increased temperature and increased concentration of reactants? <-- Correct Answer

5. Which is a property of a reaction that has reached equilibrium?
a) The amount of products is greater than the amount of reactants.
b) The amount of products is equal to the amount of reactants.
c) The rate of the forward reaction is greater than the rate of the reverse reaction.
d) The rate of the forward reaction is equal to the rate of the reverse reaction. <--Correct Answer

6. Which procedure will increases the solubility of KCl in water?
a) Stirring the solute and solvent mixture
b) Increasing the surface area of the solute
c) Raising the temperature of the solvent <-- Correct Answer
d) Increasing the pressure on the surface of the solvent

7. Given the reaction at equilibrium: N2(g) + O2(g) <-> 2NO(g) as the concentration of N2(g) increases, the concentration of O2(g) will
a) Decrease <-- Correct Answer
b) Increase
c) Remains the same
d) Increase then decrease
e) Decrease and increase

8. Given the reaction at equilibrium: 2CO(g) + O2(g) <-> 2CO2(g) When the reaction is subjected to stress, a change will occur in the concentration of
a) Reactants, only
b) Products, only
c) Both reactants and products <-- Correct Answer
d) Neither reactants nor products

9. Given the change of phase: CO2(g) changes to CO2(s), the entropy of the system
a) Decreases <-- Correct Answer
b) Increases
c) Remains the same
d) Increases then Decreases
e) Decreases then Increases

10. Given the reaction at equilibrium: 2 SO2(g) + O2(g) <-> 2 SO3(g) + heat
Which change will shift the equilibrium to the right?
a) Adding a catalyst
b) Adding more O2(g) <--Correct Answer
c) Decreasing the pressure
d) Increasing the temperature

11. The Standard Enthaply of Formation of a substance is:
a) The overall enthalpy of the reaction
b) The specific heat of a substance <--Correct Answer
c) Used in the Gibbs Free Energy Equation
d) Both B and C
e) Both A and B

12. In a chemical reaction, a catalyst changes the: -Conrad
a) Potential energy of the products
b) Potential energy of the reactants
c) Heat of reaction
d) Activation energy <-- Correct Answer
e) Changes the Activated Complex

13. Describe Specific Heat Capacity: (13-15 Peter and Vlad)
Specific heat capacity, often shortened to specific heat, is the measure of the heat energy required to increase the temperature of a of a substance by a unit of temperature.

14.Hess' Law states that:
a) Force = Mass x Acceleration
b) The Gibbs Free Energy is defined by it's equation
c) The amount of a given gas dissolved in a given type and volume of liquid
d) The heat of a reaction is the sum of it's steps <--Correct Answer
e) E=mc²

15. Collision Theory suggests that:
a) relates collisions among particles to reaction rate <--Correct Answer
b) when atoms collide, mini explosions occur
c) collisions randomly occur in a reaction
d) when two gases collide, no reaction occurs
e) relates collisions among electrons to reaction rate

16. The rate of a chemical reaction would be expected to increase the most if:
a) the activation energy doubled
b) the concentration of reactants were doubled
c) the activation energy were halved <-- correct answer
d) the surface area were doubled
e) the temperature were halved

17. The reaction that would release the least energy is:
a) condensation of a mole of water vapor <-- correct answer
b) combustion of a mole of hydrogen
c) breaking of the chlorine-chlorine bonds in a mole of Cl2(g)
d) nuclear fission in a mole of uranium
e) melting a mole of ice

18. a) For the change H2 (g) + 1/2O2 (g) ---> H2O (l), do you expect the entropy of the system to increase or decrease? Tiana (18 and 19)
Answer: H2 (g) + 1/2O2 (g) ---> H2O (l)
Changes you should notice:
gas---> liquid
1 1/2 moles ---> 1 mole
therefore, entropy decreases
b) ΔH for the above reaction is -285.8kJ/mol. Explain whether this reaction will proceed spontaneously at all temperatures or only at relatively low temperatures or at relatively high temperatures.
Answer: If entropy is negative and enthalpy is negative, look at the equation for gibbs free energy.
ΔG= ΔH - T ΔS
The only way we can get a +ve ΔG is if the temperature is really high. Therefore, the reaction will be spontaneous at low temperatures.
c) Using the molar enthalpies of formation, calculate the molar enthalpy of combustion of one mole of propane (C3H6).
Answer: C3H6 (g) + 4O2 (g)---> 3CO2 (g) + H2O(l)
ΔH= ΔHproducts- ΔHreactants
ΔH= -2058.16 kJ

19. Consider the reaction: 2C2H^ (g) + 7O2 (g)--> 4CO2 (g) + 6H2O (l) ΔH= -3119.6kJ
a) What is the enthalpy of combustion per mole of ethane, C2H6? (Ans: -1559 kJ/mol)
b)What is the enthalpy of combustion per gram of ethane? (Ans: 51.8kJ/g)
c)What is the ΔH for the above reaction of water vapour is produced instead of liquid water? The heat of vapourisation of water is 44kJ/mol.
Answer:
Heat is used up to change water from liquid to gas. ΔHvap fir H2O= 44kJ/mol
Since there is 6 H2O ..... therefore ( 6 X 44 kJ/mol) = 264 kJ would be used up to change state.
Therefore, instead of 3119.6 KJ being released... -3119.6 kJ + 264 = -2855.6 kJ

20. How do particle size, temperature, the presence of a catalyst and concentration affect the rate of a reaction?

21. What aspects of the Science Center increase it's entropy? Which decrease it? Explain your answer :)

22. Using a Maxwell Boltzman Distribution graph, explain why increasing the temperature of a system speeds a reaction.

23. Which of the following is false concerning ΔH?
a) It is the difference between the potential energies of reactants and products
b) It represents a change in potential energy
c) If the reaction consumes heat, it is positive ß answer
d) If the reaction emits heat, it is positive <--Correct Answer??
e) All of the above are true

24. Kinetic energies of atoms are: (Simone 24-26)
a) rotational
b) vibrational
c) translational
d) all of the above <---answer

25. In an open system:
a) energy and matter can move in or out <----Correct answer
b) only energy can move in or out
c) only matter can move in or out
d) neither energy nor matter can move in or out

26. The rate determining step:
a) is the slowest step in a reaction mechanism <---answer
b) is the fastest step in a reaction mechanism
c) does not exist
d) encompasses all the steps in a reaction mechanism